Not a duplicate of Hydrazine synthesis - I know what hydrazine is and am not going near it voluntarily!
Looked at this resource on the Internet which cites three major commercial-scale processes:
- $\ce{H_2O_2}$ process (in use at Arkema and Mitsubishi Gas Chemical, developed by Produits Chimiques Ugine Kuhlmann and patented in 1976)
- Bayer process (at the eponymous company)
- Urea process
What processes do other major large-scale producers use and what are the driving forces behind adoption of a particular hydrazine synthesis? I can guess that Chinese producers may use the urea process, but I'm not sure.
Background: am a Space Exploration.SE regular and am interested in learning more about worldwide production of hypergolic propellants.